1. Field of the Invention
The present invention relates to a method for preventing edge chipping and cracking damage encountered by semiconductor chips in a die picking operation during separation from an adhesive sheet. Moreover, the invention also relates to a device for preventing potential edge chipping and cracking damage encountered by a semiconductor chip during die picking processes.
Currently in the technology, in effectuating semiconductor chip pickup processes separating chips which adhere to an adhesive shorter film, initially a semiconductor wafer, which may or may not have operative components provided thereon, is diced and divided along suitable dicing lines and division lines in order to form a plurality of semiconductor chips, while adhered to the adhesive sheet. Normally, these semiconductor chips are adhered to the underlying adhesive sheet or film prior to and during dicing from the wafer, and each of the individual semiconductor chips is then subsequentially picked from the adhesive tape and separated therefrom in order to enable the individualized semiconductor chips to be further processed, as is well-known in the technology. This further processing may entail, for example, conveying the semiconductor chips subsequent to their separation from the adhesive sheet to being mounted on a lead frame or TIB tape, and then effecting a mounting process for sealing the product into a package so as to complete an electronic or semiconductor device.
In the present technology, the individual diced chips are normally separated from the underlying adhesive tape on which the chips are positioned through the employment, for example, of suctioning devices or collets, which may include an aspirating or suctioning nozzle located above the chips, and which will lift the semiconductor chips in sequence so as to enable separation thereof from the underlying adhesive sheet. However, this known method and apparatus may, at times, result in the adhesive sheet tearing, and possibly remain adherent to the semiconductor chips, particularly to the chip edges, so as to cause the thereby engaged semiconductor chip to possibly tilt or be misplaced and subjected to edge chipping or cracking. This may then render the semiconductor chip defective and unable to be employed in an electronic package.
Consequently, pursuant to advances in the technology, methods and semiconductor chip pickup devices have been developed in which chucks or jigs are positioned beneath an adhesive sheet or tape having the diced semiconductor chips located therein, and wherein the device incorporates upstanding pin members engaging the lower surface of the adhesive sheet. The pin members are adapted to be displaced upwardly while, concurrently, a vacuum or subatmospheric pressure is applied below the adhesive sheet, which will tend to cause the sheet to be adhered to the upper ends of the pins and during a subsequent downward motion of the chuck or jig cause the film to be pulled away and separated from the semiconductor chips. This will then enable the thus separated semiconductor chips to be raised by the suctioning collet, or any suitable lifting device, and to be transported for further processing.
2. Discussion of the Prior Art
Although these various devices, as presently used in the technology, effect the foregoing at different degrees of efficacy, these have not fully been successful in eliminating potential edge chipping or cracking of the semiconductor chips during separation from the underlying adhesive tapes or sheets, inasmuch as the semiconductor chips may still be subject to edge damaging due to the adhesive tape or sheet snapping back or tiling the chips during the separation or picking process.
Kurosuwa, U.S. Pat. No. 6,709,543 B2, discloses a semiconductor chip pickup device and pickup method, wherein a plurality of upstanding pin members, which are mounted on a chuck or jig located beneath an adhesive sheet or tape that has the semiconductor chips adhere to the upper surface thereof. During upward motion of the pin members, the adhesive sheet is displaced upwardly, while concurrently a vacuum or sub-atmospheric pressure is created beneath the adhesive sheet so as to assist in the pulling away and separation thereof from the superimposed semiconductor chips. In this publication, the pin member arrangement includes a plurality of somewhat shorter pins inwardly located of externally lengthier and higher extending in order pins to assist in the deflection of the adhesive sheet. Although this is generally deemed to be a workable chip picking apparatus and method, the shorter pins are constructed so as to be adjustable in height relative to the fixed lengthier pins, thereby considerably increasing the complexity and cost of the chip pickup device, while still not having deemed to provide a complete degree of control in the prevention of adhesive tape snapback which could conceivably damage the edges of the superimposed and being presently separated semiconductor chip.
Kurosawa, et al., U.S. Pat. No. 6,555,418 B2 disclose a method and apparatus for separating or picking up semiconductor chips or elements from an underlying adhesive sheet on which the semiconductor elements are adhesively positioned by means of a pushup device. The latter comprises pin members, which penetrate through openings in a vacuum device, in which a controlled vacuum is created to draw the adhesive sheet downwardly onto the pin member away from contact with the semiconductor chip, while the latter is raised by means of a vacuum collet structure.
Tawara, U.S. Pat. No. 6,386,815 B1 discloses a pickup apparatus for semiconductor chips wherein a cam structure permits for rotatable arrangement of a lower chuck member so as to be adjustable to differently sized semiconductor chips, which are to be picked up and separated from an underlying adhesive tape or film through the intermediary of differently sized and displaceable pins without having to replace a pin holder. This does not provide for any structure or method which will prevent adhesive tape or sheet snapback which would possibly have a tendency to cause edge cracking or chipping of the semiconductor chip while being separated or picked up from the underlying adhesive tape or sheet.
Finally, Matsui, et al., U.S. Pat. No. 5,589,029 discloses an arrangement for piercing through adhesive tape by means of upstanding displaceable pins so as to engage the bottom of a semiconductor chip, which is being upwardly drawn by means of a vacuum collet, while concurrently providing a sub-atmospheric or vacuum atmosphere below the adhesive tape to assist in drawing the latter downwardly into contact with a chuck below the collet, and aid in separating the adhesive sheet from the semiconductor chip. This type of structure would not, in effect, prevent any snapback of the adhesive sheet during separation from the semiconductor chip and may possibly lead to edge cracking or chipping of the chip as it is being picked or separated from the adhesive sheet.